3D blastocyst illustrationIn spite of a wealth of medical knowledge surrounding the process of reproduction, one aspect of embryo development — its implantation in the uterus — has remained a mystery. Now, however, researchers at the University of Cambridge say they’ve not only discovered the “black box” of embryo implantation, they’ve filmed it in action. The discovery is so stunning that the research team expects textbooks will need to be updated to include this once-missing link.

Professor Magdalena Zernicka-Goetz and Dr. Ivan Bedzhov led the Cambridge team to the discovery of what happens during the roughly two days it takes a fertilized egg to become an embryo. The answer to the mystery seems to be the shape of the egg / embryo.

In mammals, embryos have been thought to occur in a two-step process. During the first phase, a blastocyst develops. This small ball of cells floats freely in the female reproductive organs, until implantation. Blastocysts can be grown in a laboratory setting and studied easily outside the body.

After implantation, the blastocyst experiences a burst of activity that changes it from a tiny ball into a cup-shaped embryo. Studying embryos outside the body is almost impossible because, by its very nature, it is now a part of the female body.

Using the cells of female mice for their study, the Cambridge researchers created an environment in the lab that mimics that of a uterus. They used a gel base blended with the correct balance of chemicals and biological properties and degree of elasticity that would allow blastocysts to act as if in the womb. One very important aspect of the artificial uterine environment was transparency. Because optical light could pass through the transparent gel, it was possible to film blastocyst activity as it occurred.

The researchers watched as a third, middle, phase of the process unfolded. The blastocyst goes from being round like a ball into a rosette of wedge-shaped cells before developing the cup-like shape of the implanted embryo. Zernicka-Goetz describes the rosette shape, which had never been seen before, as “a beautiful structure.”

In further describing the transformation, Zernika-Goetz says, “This rosette is what a mouse looks like on the 4th day of its life, and most likely what we look like on the 7th day of ours.” She adds, “It’s fascinating how beautiful we are then and how these small cells organise so perfectly.”

Currently, textbooks on developmental biology take merely an educated guess at the process of implantation. Zernicka-Goetz says, “We now know that what I learned and what I teach...was totally wrong.”

In addition to filling in gaps in textbooks, the Cambridge study may lead to advances in in-vitro fertilization (IVF) and stem cell knowledge for regenerative medicine.

Source: Zernicka-Goetz, Magdalena, and Ivan Bedzhov. “Rewriting the text books: Cambridge cracks open ‘black box’ of development.” University of Cambridge Research. University of Cambridge. Feb 13, 2014. Web. Mar 13, 2014.